Hatch construction in a low temperature liquid tank

ABSTRACT

A hatch construction in a low temperature liquid tank having a heat insulating layer inside a tank shell, characterized in that a hatch dome having a cover and inside an inner heat insulating layer is adapted for upward and downward movement slidably through an opening formed in the top wall of said tank shell, said hatch dome being carried by supports on the upper surface of the top wall of the tank shell, and a heat insulating seal means is provided for airtightly coating a space between the hatch dome and the peripheral part of said opening.

ted States Patent [191 Katsuta et a1.

[ Dec. 23, 1975 [22] Filed: June 7, 1974 [21] Appl. No.: 477,420

[30] Foreign Application Priority Data June 22, 1973 Japan 48 70553 [52] US. Cl. 220/9 LG; 222/385; 114/74 A [51] Int. Cl. B65D 25/18 [58] Field of Search 222/333, 131, 385;

220/9 LG, 15; 114/74 A, 74 T, 201

[5 6] References Cited UNITED STATES PATENTS 3,064,612 11/1962 Gardner et al 114/74 A 3,304,877 2/1967 Carter et a1 114/74 R Primary Examiner-Stanley H. Tollberg Assistant Examiner-Hadd Lane Attorney, Agent, or Firm--McGlew & Tuttle [5 7] ABSTRACT A hatch construction in a low temperature liquid tank having a heat insulating layer inside a tank shell, characterized in that a hatch dome having a cover and inside an inner heat insulating layer is adapted for upward and downward movement slidably through an opening formed in the top wall of said tank shell, said hatch dome being carried by supports on the upper surface of the top wall of the tank shell, and a heat insulating seal means is provided for airtightly coating 21 space between the hatch dome and the peripheral part of said opening.

5 Claims, 5 Drawing Figures US. Patent Dec.23, 1975 Sheet10f2 3,927,787

FIG.1

U.S. Patent Dec.23, 1975 Sheet2of2 3,927,787

HATCH CONSTRUCTION IN A LOW TEMPERATURE LIQUID TANK Low temperature liquid tanks generally have hatches on the top walls of. the tank adapted to contain gas inlet pipes to inactivate the tank, pipes for low temperature liquid in the tank, spray pipes to pre-cool the inside of the tank, pipesfor carrying the liquid out of tank in emergency wirings for pumps, ladders and the like.

In the known type of the storage tank for keeping a low temperature liquid therein, it has been a disadvantage that much larger heat stress is applied to an inner heat insulating layer c which maycause a loss, or damage-on curved portions 6 due to integrated construction of a hatch dome a and a tankshell b as can be seen from FIG. 1.

Other problem is the difficulty of airtightly sealing a cover e since a flange d of the hatch may deform irregu larly due to low temperature of the liquid.

It is a primary object of the invention, therefore, to eliminate the above drawback such that the low temperature liquid tank may encounter in usual time.

Another object of the invention is to provide a hatch construction in the low .temperature liquid tank in which the hatch dome and its peripheral top walls can respectively freely has heat contraction, so that the inside heat insulating layer and hatch dome cover may not be adversely affected.

Thus, the hatch construction in the low temperature liquid tank according to the invention comprises, for

the objects as above described, a hatch dome which is enclosed by a cover with an insulating layer lined inside, the hatch dome being inserted and slidably movable through an opening upward and downward in the top wall of the tank shell, wherein the hatch dome is carried by supports on the upper surface of the top wall,

of the tank shell and means is provided for sealing airtight a space between the hatch dome and the peripheral edge of the opening in the top wall in heat insulation.

In the hatch construction of the invention, the hatch dome carried by supports on the upper surface of the top wall of the tank shell can slide upward and downward through the opening in the top wall of the tank shell and avoids concentration of a stress force in the inner heat insulating layer during expansion or contraction of the hatch dome depending on the variation of temperature, the hatch dome being prevented from irregular deformation or from troubles in keeping airtightness in the dome cover.

Thus, in the hatch construction of the invention, the space between the hatch dome and the peripheral edge of the opening in the top wall of the tank shell is sealed airtightly fully with a heat insulating seal means, which preferably is a flexible membrane permitting upward and downward movement of the hatch dome so as to isolate the interior of the tank from atmosphere, and heat insulation of the space is kept up advantageously by the flexible membrane which is filled with a heat insulating material.

Other features and objects of the invention will become apparent from the description by way of example Oman embodiment of the invention with reference to the accompanying drawings in which:

FIG. 1 is a view in cross section of a hatch construction of a conventional low temperature liquid tank;

FIG. 2 is a transverse cross section of a ship hull having a low temperature liquid tankprovided with a hatch construction as in a preferred embodiment of the invention;

FIG. 3 is a cross section of the hatch construction of the tank according to the invention;

FIG. 4 is a view illustrating the lower end of a liquid discharge pipe provided in the hatch construction of FIG. 3; and

FIG. 5 is an enlarged view of a connection between an outlet pipe and a liquid discharge pipe.

Now referring to FIG. 2, -a ship hull is shown in a transverse cross section, which includes a low temperature liquid tank having the hatch construction of the invention. The ship hull is provided with an impermeable layer 3 of alow-temperature resistant material having a heat insulating layer 2 made of foam resin or the like inside the tank shell 1 or the ship hull. On the top wall In of the tank shell 1 is provided a hatch dome 4 and 4'. The tank shell 1 has on left and right sides and also on lower side ballast tanks 5.

A low temperature liquid 6 is contained in the tank shell 1 close in contact with the'impermeable layer 3 inside the tank. This low temperature liquid 6 can be discharged outwards through a liquid discharge pipe 8 and hatch dome 4 by means of a submerged pump 7. Power is supplied to pump 7 over wiring 9.

A safety valve 10, a low temperature liquid transport pipe 11, nozzle pipes 12 and 13 to cool the tank, and a ladder 14 are all retained by the cover of other hatch 'dome 4'.

FIG. 3 illustrates details of a construction in the outer peripheral part of the hatch dome 4. As may be seen in the figure, the hatch dome 4 is inserted to slide in an opening of the top wall lain the .tank shell. The hatch dome 4 is carried by a plurality of supports on the upper surface of the top wall la in the tank shell.

Each support 15 is at its lower end connected pivotally to an eye 16 secured to the periphery of the opening in the top wall of the tank shell, and the upper end to an eye 17 secured to the outer periphery in the upper part of the hatch dome 4.

Inside of the hatch dome 4 is lined with a heat insulating layer 18. A cover 20 is airtightly fitted with a fastening bolt 19 to an upper flange 4a of the hatch dome 4, a heat insulating layer 21 being also provided on the inside of the same cover 20.

The cover 20 is provided with a liquid discharge pipe 8 passing there through and it is airtightly secured thereto by welding. An outer extension of the pipe 8 is wound with a heat insulating material 22. If necessary the liquid discharge pipe 8 may be formed of a double tube.

Covering a space 23 airtightly between the hatch dome 4 and the top wall la of the tank shell from upward, there is provided a flexible membrane 24 of an impermeable material. An upper edge 24a of the membrane 24 is rigidly fixed to the outer peripheral surface of the hatch dome 4 and a lower edge 24b is secured to an upper surface of the top wall Ia of the tank shell.

The flexible membrane 24 is filled with a heat insulating material 25 inside the membrane. Preferably the flexible membrane 24 may be made of stainless steel, rubber, or teflon and the heat insulating material 25 inside the membrane of a. polyurethane foam, rock wool, parlite or like material.

FIG. 4 shows a part of the lower end of the liquid discharge pipe 8. As seen in the figure, the discharge pipe 26 of the submerged pump 7 is connected to a lower end of the liquid discharge pipe 8 being slidably inserted into the pipe 26. In a gasket housing 27 at the upper end of the discharge pipe 26 is contained a gasket 29 which may be pressed by gasket push 28 to the outer peripheral surface of the liquid discharge pipe 8. The gasket 29 may preferably be made of teflon, tetrafluoropolyethylene copolymer, aluminum or copper of the low temperature resistivity.

The submerged pump 7 is fixedly provided on a mounting 30 with the heat insulating material secured to a bottom surface of the tank shell 1. A heat insulating layer 31 provided further on the heat insulating layer 2 inside the tank shell 1 can shelter the lower part of the submerged pump 7.

The construction of the hatch dome 4 as above de scribed also can be used in other hatch dome 4.

When the low temperature liquid 6 is contained in the tank and the temperature in the tank rises approximately to a boiling point (l62C in case of methane) of the low temperature liquid 6, the inner heat insulating layer 2 in the top wall 1a of the tank shell will contract in the way as shown by broken line A and the inner heat insulating layer of the hatch dome 4 also will contract with the hatch dome 4 indicating a deformation as shown by broken line B.

Since the tank shell 1 and its inner heat insulating layer 2, and the hatch dome 4 and its inner heat insulating layer 18, respectively, are independent from each other, it is not possible for each heat insulating layer 2 and 18 to receive a stress force concentrated or any crack caused in them.

The airtight coating of the flexible membrane 24 over the space 23 may avoid an evaporated gas to leak or mixing of air into the tank even through the low temperature liquid 6 may be a liquefied gas of a flammable nature. Also, presence of the heat insulating material 25 will keep the flexible membrane 24 to remain approximately in the normal temperature and will avoid the membrane being degraded of resiliency due to the low temperature.

The cover for the hatch dome 4 can be fitted easily to the hatch dome 4, because possible deformation of the hatch dome 4 is smaller in the amount and such deformation may not be irregular even when it 4 occurs. Up-and-down movement of the liquid discharge pipe 8 following the heat deformation of the tank shell 1 and hatch dome 4 or elongation and contraction of the discharge pipe 8 from temperature change may not cause any trouble, since the lower end of the liquid discharge pipe 8 is connected slidably to the upper end of the discharge pipe 26 of the pump 7.

Thus, in the hatch construction according to the invention, cracks or breakage in the inner heat insulating layer may be fully avoided which could occur as the disadvantage in the known inner heat insulating tank in use for the low temperature liquid. The tank cover can be fitted most securely to the hatch dome to retain a high safety.

We claim:

1. A hatch construction for a low temperature liquid tank having a tank wall with heat insulation on its interior and a hatch opening through said tank wall, comprising a tubular hatch dome extending through the opening and having an outer upper end, supporting means for supporting the hatch dome on said tank connected between said tank wall and said dome at a location on said dome spaced above said tank wall, and heat insulation seal means connected between said tank wall and said hatch dome at a spaced location above said wall and below the connection of said support to said hatch dome and extending around the periphery of said hatch dome and sealing and insulating between said hatch dome and said plate.

2. A hatch construction according to claim 1, wherein said insulation sealing means includes a sealing membrane sealed at its one end to said hatch dome and at is opposite end to said tank wall.

3. A hatch construction according to claim 2, wherein said seal means including a mass of heat insulation dispose in a space between said membrane and the enclosed spaced of said hatch dome and said hatch wall.

4. A hatch construction according to claim 1, wherein said supporting means comprises a plurality of individual supporting members connected between said hatch dome and said hatch wall, said hatch dome and said hatch wall having eyelets engageable with respective ends of said supports.

5. A hatch according to claim 4, wherein said support comprises a rigid member pivoted at each end in the respective eyelet. 

1. A hatch construction for a low temperature liquid tank having a tank wall with heat insulation on its interior and a hatch opening through said tank wall, comprising a tubular hatch dome extending through the opening and having an outer upper end, supporting means for supporting the hatch dome on said tank connected between said tank wall and said dome at a location on said dome spaced above said tank wall, and heat insulation seal means connected between said tank wall and said hatch dome at a spaced location above said wall and below the connection of said support to said hatch dome and extending around the periphery of said hatch dome and sealing and insulating between said hatch dome and said plate.
 2. A hatch construction according to claim 1, wherein said insulation sealing means includes a sealing membrane sealed at its one end to said hatch dome and at is opposite end to said tank wall.
 3. A hatch construction according to claim 2, wherein said seal means including a mass of heat insulation dispose in a space between said membrane and the enclosed spaced of said hatch dome and said hatch wall.
 4. A hatch construction according to claim 1, wherein said supporting means comprises a plurality of individual supporting members connected between said hatch dome and said hatch wall, said hatch dome and said hatch wall having eyelets engageable with respective ends of said supports.
 5. A hatch according to claim 4, wherein said support comprises a rigid member pivoted at each end in the respective eyelet. 